1. Field of the Invention
The present invention is in the field of imaging devices. More particularly, the present invention is in the field of imaging devices which provide a visible image from invisible infrared radiation. Still more particularly, this invention is in the field of devices, which on a moving scanning platform includes optics for receiving infrared radiation and directing this radiation to an electronic detector including plural photo-conductive pixel elements. The pixel elements are responsive to infrared radiation to substantially simultaneously record image information from an image line of the scene. Each image line has a width of one pixel so that a series of lines side by side can build up an image mosaic similarly to the way a television picture is created. Sequential image lines are recorded so that the entire scene is recorded as the scanning platform moves. Adjacent image lines cooperatively form a mosaic image of the scene viewed through the scanner optics. As the imaging scan progresses, simultaneous analogue image information from the pixels of the electronic detector is stored, is then sequentially fed out, and is converted to analog serial information. This analog serial information is converted to parallel digital information, and then to serial digital information for imposition upon a light beam coupling the information off of the moving scanning platform.
This light beam is received by a receiver on a stationary base or housing without the use of slip rings, flexible signal-carrying conductors, or other physical signal-carrying structure extending between the moving scanning platform and the stationary parts of the scanner. On the scanner base, the receiver connects the optical output signal received from the moving platform of the scanner to a facility, which can be selectively varied in its configuration, for conversion into an electrical signal. This resulting electrical image signal is further processed to provide image information in a variety of forms. The resulting image information may be stored for later analysis or viewing, and also may be presented in near real-time on a viewing screen, such as on a computer CRT or LCD screen, or on a television set, dependent upon the configuration(s) selected for the conversion facility.
2. Related Technology
Conventional optical scanners have been known which use an optical system with rotating mirrors and a fixed, single-pixel detector. Other conventional optical scanners have used similar optical systems along with fixed, high-cost, HgCdTe multi-pixel detector arrays. These conventional scanners have generally relied on reciprocating or oscillating optical scanning apparatus with a fixed detector. Inherently, alignment problems arise between a moving optical system (i.e., the scanning mirror and associated lenses), and the stationary infrared radiation detector. These alignment problems seriously compromise the performance of such a scanner, and result in a trouble-prone system which requires frequent maintenance and adjustments.
The conventional optical scanners also used sensors which were of high cost; involved a considerable level of complexity; have very complex, expensive, and possibly trouble-prone rotating, oscillating, or reciprocating mirror systems; and had a high initial acquisition cost and high maintenance costs. As an example only, the conventional technology would provide an infrared scanner with a moving optical system delivering infrared radiation from a scene to be imaged to a fixed photovoltaic detector. The detector would be cooled by a cryostat or cryocooler, so that the complexity of this cooling apparatus must also be considered in the overall complexity and cost of the imaging system. This conventional imager would also potentially have difficulties or require high maintenance because of the stringent alignment requirements between the scanner and detector. Also, the conventional system would have an initial acquisition cost of about $300,000 to $400,00 dollars. In contrast, the present infrared line-scanning imager achieves a number of cost-reducing simplifications and improvements which can provide an infrared line-scanning imager of comparable performance at an initial cost of about $50,000, in equivalent quantities.